DE19738804B4 - Fuel injection device for internal combustion engines - Google Patents

Abstract

Fuel injection device for internal combustion engines, with a fuel from a low pressure chamber (5) via a high pressure line (3) to a high pressure pump (1) delivering a fuel injection valve (7) and a hydraulic transmission device (13) between the high pressure pump (1) and the fuel injection valve (7), which has a stepped piston (19) displaceable in a bore (15), the end faces of which each delimit a pressure chamber, a first larger end face (21) having a first pressure chamber (23) connected to the pump-side part of the high-pressure line (3) and a second opposite one smaller end face (25) delimits a second pressure chamber (27) connected to the part of the high-pressure line (3) on the injection valve side, and with an inlet channel containing a pressure valve for filling the second pressure chamber (27) with fuel, characterized in that the pressure in the second pressure chamber ( 27) opening inlet channel from the first pressure pipe m (23), and is formed by a through hole (43) in the stepped piston (19), the pressure valve closing the inlet channel being arranged inside the stepped piston (19), the transmission ratio on the stepped piston (19) between the ...

Description

The invention is based on a fuel injection device for internal combustion engines according to the preamble of claim 1. In such a case from Scripture DE 41 18 237 A1 Known fuel injection device, fuel is delivered from a low pressure chamber via a high pressure line to a fuel injection valve by means of a high pressure pump. A hydraulic booster between the high-pressure pump and the fuel injection valve is provided for increasing the pressure on the fuel injection valve. This hydraulic transmission device has a stepped piston which is displaceable in a bore, the end faces of which each delimit a pressure space, a first larger end face delimiting a first pump-side pressure space and a second smaller end face delimiting an injection-side pressure space. The hydraulic pressure transmission at the transmission device is dependent on the area ratio of the pump piston end faces adjoining the pressure chambers, the actuation of the stepped piston being effected via the high-pressure fuel supply on its larger piston end surface.

Filling the injection side Pressure chamber on the small end face of the step piston of the transmission device is done via a valve assembly from the fuel circuit of the injector. The return movement the stepped piston is also hydraulic via the fuel circuit and a corresponding valve arrangement in a feed line in the Restoring chamber performed.

The known fuel injection device for internal combustion engines the disadvantage of being required a large number of control valves and thus a complicated one Has structure. Also needed the known fuel injector due to the complicated Valve control requires a large amount of space, which is common to modern internal combustion engines frequently not available is.

Another disadvantage of the translation facility at the known fuel injection device is the large volume to be displaced in the storage room, that the efficiency of the translation device significantly reduces.

The fuel injection device according to the invention for internal combustion engines with the features of the characterizing part of the claim 1 has in contrast the advantage that the Injection pressure at the fuel injector and the hydraulic one Efficiency as a ratio of injection energy and supplied Work of the entire injector can be increased without compared to injection systems without translation facility Enlarging installation space significantly. Additionally points the fuel injection device according to the invention across from known fuel injection devices with a translation device the advantage of a significantly lower construction and assembly effort due to the simple construction. This will be done especially possible because that the Inlet pipe is provided as a through hole in the stepped piston is what has the advantage that the translation device builds very small. this makes possible retrofitting the translation facility in existing fuel lines on known injection systems, such as distributor pumps, pump-line-nozzle systems or common rail systems. The filling valve used in the feed line is preferably a pressure valve as a check valve trained, the opening pressure on the Valve spring is adjustable. The step piston of the transmission device is possible with one long sliding surface in the pilot hole arranged, which advantageously means little fuel from the pressure rooms about that Play between the stepped piston and its guide bore, whereby the translation facility has only slight leakage losses. The transmission ratio on Step piston is preferably in a ratio of the larger end face to smaller face between 1 to 3, with gear ratios between 1.5 and 2.2 are particularly peculiar, since the hydraulic efficiency is there without significant increases in the necessary delivery volume of the high pressure pump significantly increased.

This increase in efficiency becomes energetic a higher one Importance assigned, as a pure pressure increase at the injection valve, because with the reduced need for drive energy also thermal The load on the pump and thus its tendency towards so-called "feeders" decreases Games between pistons or distributor shafts and their bushings realized be so that by minor leaks the efficiency can be increased again can.

Another benefit is that Integrate the rod filter into the inlet channel to the injection side Pressure chamber is reached because the dead volume in the injection-side high-pressure area can be reduced again.

That on the piston ring face of the Spring space volume displaced by the stepped piston becomes more advantageous Way, if possible without back pressure, relieved in the low pressure circuit so that hydraulic Loss of the translation facility preferably can be kept small.

For a safe function, a throttle point is also provided within the inlet line in the injection-side pressure chamber, which is large enough to be refilled at the back To ensure running step piston and which is small enough to build up a pressure difference during the pressure transfer stroke of the step piston, which closes the check valve quickly. This separate throttling point can be omitted if the rod filter is inserted before the check valve, the gaps of which are designed in such a way that they perform the necessary throttling.

The reset of the step piston the translation facility is advantageously carried out by means of a return spring, so that none additional hydraulic restoring forces necessary are. It can also be used for additional Control lines and control valves are dispensed with, making the constructive structure of the translation device is simplified again.

Another advantageous embodiment of the Fuel injection device according to the invention is the provision of the stepped piston in a guide bush, which in turn is in a Pipe socket is used. The guide bushing has longitudinal slots through it Connection element, preferably protrudes through a clip and engages radially on a shoulder of the stepped piston. Radially outside the guide bushing grips the return spring of the stepped piston, which is in an annular space between the guide sleeve and the inner wall of the pipe socket is guided. This enables Spring arrangement a large Return spring winding diameter and therefore great Spring travel. In addition, the components of the translation device, as Simply manufacture rotationally symmetrical parts, which reduces the manufacturing effort and the needed Installation space significantly reduced. The bypass channel is more advantageous Integrated into the guide bush the pressure chamber opening towards the injector side Pressure valve is upstream of a throttle. Here is the Bypass channel as a simple longitudinal bore trained in the guide bush and flows out through hole extensions the guide bore receiving the stepped piston in the guide bush in the respective pressure rooms. The stepped piston can, as in the exemplary embodiment shown be formed in one piece, due to a simpler production it is, however, advantageous to design the stepped piston in two parts analogous to the construction shown without changes.

Another advantage of the fuel injection device according to the invention is made possible by the close arrangement of the translation device on Fuel injector reached, so the area with very high Fuel pressures can be limited to a very small line area in which this high pressure actually needed becomes. The damage volume in the high-pressure injection area and thus the hydraulic loss work can be reduced. Furthermore, pump-side fuel line area, the pressure remains reduced, which results in lower component stresses there, so that this can be dimensioned smaller with the same long service life.

The translation facilities of Individual fuel injection valves can be connected to each other and the connection to the high-pressure fuel pump can be via a joint management.

Other advantages and beneficial Embodiments of the subject matter of the invention are the description, the drawing and the patent claims.

Three embodiments of the fuel injection device according to the invention for internal combustion engines are shown in the drawing and are described in the following description explained in more detail.

They show 1 a first embodiment of the fuel injection device, in which the inlet line in the injection valve-side pressure chamber is formed by a through hole in the stepped piston of the transmission device, the 2A and 2 B a second embodiment in two views, in which the inlet line is formed in the pressure chamber on the injection valve side by a bypass channel running parallel to the stepped piston 3A and 3B a third embodiment in two positions of the step piston, in which the feed line is arranged in a guide bushing receiving the step piston, which in turn is inserted into a pipe socket and the 4 a single view of the return spring and the stepped piston connecting bracket in the third embodiment.

description of the embodiments

The in the 1 The illustrated fuel injection device for internal combustion engines has a high-pressure fuel pump 1 on that fuel through a high pressure line 3 from a low pressure room 5 , preferably a fuel tank to a fuel injection valve 7 promotes. For controlling the high-pressure fuel supply to the injection valve 7 is a control valve in the described embodiments 9 , preferably a solenoid valve, into one of the high pressure line 3 branching bypass line 11 used as a return line in the low pressure room 5 empties. The control valve 9 one towards the low pressure room 5 opening check valve 12 downstream downstream, through which there is a remaining stand pressure in the bypass line 11 and the high pressure line 3 can be adjusted.

Here is the control valve 9 to switch so that that of the high pressure pump 1 delivered fuel with closed control valve 9 to the injector 7 flows or via the open control valve 9 via the bypass line 11 in the low pressure room 5 flows back (short circuit), whereby that in the bypass line 11 arranged check valve 12 maintains a certain stand pressure in the system.

To increase the injection pressure at the injection valve 7 is a hydraulic translation device 13 into the high pressure line 3 between the high pressure pump 1 and the injector 7 used. This hydraulic translation device 13 has one in a guide hole 15 of a housing 17 axially guided step piston 19 on, each with its axial end faces a pressure chamber in the bore 15 in the housing 17 the translation facility 13 limited. A first larger end face delimits 21 of the step piston 19 a first pressure room 23 which on the other hand with the high pressure pump 1 leading part of the high pressure line 3 connected is. A second, smaller face 25 of the step piston 19 delimits a second pressure chamber 27 in the housing 17 the translation facility 13 which is the first pressure room 23 opposite and that with a second, with the injector 7 connected part of the high pressure line 3 connected is. The one-part stepped piston shown in the first exemplary embodiment has 19 at its cross-section transition from a large diameter D1 to a small diameter D2 an annular collar 29 that protrudes beyond the large diameter D1. With its ring face facing away from the large diameter range on the stepped piston 31 limits the ring collar 29 towards the second pressure chamber 27 a spring chamber 33 which, on the other hand, by one of the second pressure chamber 27 in the hole 15 in the housing 17 pressed sleeve 35 is limited. This limits the stepped piston 19 with its small diameter D2 axially leading inner wall surface of the sleeve 35 the second, injection-side pressure chamber 27 , The the spring chamber 33 delimiting ring face on the sleeve 35 also serves as a spring support surface for one in the spring chamber 33 clamped return spring 37 that on the ring face 31 of the ring band 29 of the step piston 19 attacks and this with the ring collar 29 in contact with a housing-fixed bore shoulder 39 the hole 15 in the housing 17 holds. From the spring chamber 33 preferably carry two relief lines 41 starting in the low pressure room 5 lead. For filling the second, injection-side pressure chamber with fuel 27 is an axial through hole 43 in the stepped piston 19 provided by the first pressure chamber 23 starting in the second pressure room 27 empties. It is in this through hole 43 a check valve serving as a filling control valve 45 used, the valve member 49 against the closing force of a valve spring 47 towards the second pressure chamber 27 from a valve seat 51 can be lifted off. Furthermore, a fuel filter designed as a rod filter 57 to the first pressure room 23 adjacent area of the through hole 43 in the stepped piston 19 used, the filter columns are designed so that in addition to the fuel filtering for the function of the translation valve 13 required throttling takes place.

This is due to the diameter D1 to D2 on the first face 21 and the second face 25 certain transmission ratio on the stepped piston 19 lies in a value range from 1 to 3 and should preferably have a value between 1.5 and 2.2.

The fuel injection device according to the invention works in the following way.

Before the start of high pressure injection on the fuel injector 7 becomes the second pressure room 27 over through the through hole 43 in the stepped piston 19 formed feed line filled with fuel. This is done by filling the pressure chamber 27 until the interconnected pressure rooms 23 and 27 there is pressure equalization so that the check valve 45 closes the inlet line. Injection at the injector 7 is initiated when the control valve 9 the bypass line 11 closes and the high pressure pump 1 into the high pressure line 3 to the injector 7 promotes. As a result, the high-pressure fuel initially flows into the first pressure chamber 23 on the stepped piston 19 the hydraulic translation device 13 and moves the stepped piston 19 towards the smaller second pressure chamber 27 , It comes as a result of the different ring faces 21 . 25 of the step piston 19 to a pressure increase in the second pressure room 27 compared to the fuel pressure built up by the high pressure pump. This increased fuel pressure passes through the second part of the high pressure line 3 to the injector 7 and there at the injection openings for injection into the combustion chamber of the internal combustion engine to be supplied. The one in the spring chamber 33 Any fuel present is discharged via the relief lines without any significant back pressure 41 hardly displaces and reduces the efficiency of the translation device 13 , The check valve 45 is held back with the force resulting from the excess from the pressure chamber 27 effective pressure force and the spring force of the valve spring 47 opposite that of the pressure room 21 effective pressure force results. This leaves the check valve 45 during the working stroke of the stepped piston 19 locked.

High-pressure fuel injection at the injection valve 7 is ended by the control valve 9 the bypass line 11 opens again so that the high pressure line 3 over this with the low pressure room 5 is connected and in the high pressure line 3 and thus in the translation facility 13 high fuel pressure up to an adjustable stand pressure in the low pressure chamber 5 relaxed. This is over the check valve 12 in the bypass line 11 adjustable remaining pressure in the high pressure line 3 above the opening pressure of the check valve 45 so that the second pressure room 27 during the return movement of the stepped piston 19 again with fuel from the first pressure chamber 23 through the through hole 43 is filled. The step piston is reset 19 mainly by the force of the return spring 37 that the stepped piston 19 with his ring collar 29 in contact with the housing-fixed bore heel 39 and thus moved back to its starting position. The fuel is discharged from the first pressure chamber 23 in the second pressure room 27 on the fuel filter 57 , which is designed as a rod filter.

The second exemplary embodiment of the fuel injection device according to the invention for internal combustion engines differs from the first exemplary embodiment only in the design of the transmission device 13 in the high pressure line 3 which is why the 2 on the representation of the translation facility 13 is limited. The shows 2A the second embodiment of the translation device 13 in a sectional view and the 2 B the translation facility 13 in a view rotated by 90 degrees 2A ,

The translation facility 13 of the second embodiment differs from the translation device 13 the first, in the 1 illustrated embodiment in the arrangement of the supply line from the first, pump-side pressure chamber 23 in the second, injection valve-side pressure chamber 27 on the now two-part stepped piston 19 , This is an inlet or filling channel for the second pressure chamber 27 formed in the second embodiment as a bypass line, which is parallel to the stepped piston 19 in the housing 17 the hydraulic translation device 13 is arranged. The bypass line is through one of the first pressure chamber 23 laxative first cross hole 59 and one from the second pressure room 27 laxative second cross hole 61 formed by a longitudinal bore 63 are interconnected, which are preferably axially parallel to the stepped piston 19 runs. There are in this longitudinal bore 63 analogous to the through hole 43 in the stepped piston 19 in the first embodiment, the check valve 45 and the Kratstoffilter 57 used.

The in the 2 Hydraulic translation device shown 13 works in the same way as in the 1 shown translation device 13 the fuel injection device according to the invention. The transmission ratio at the translation facility 13 is in turn determined by the area ratio of the end faces 21 and 25 on the stepped piston 19 to each other and is also in a range from 1 to 3, preferably in a range from 1.5 to 2.2.

In the in the 3A and 3B The third exemplary embodiment shown is the stepped piston 19 in a guide hole 65 a guide bush 67 slidably guided, which in turn in a pipe socket 69 is used. The stepped piston limits 19 with its larger face 21 the first pressure chamber on the pump side 23 and with its smaller face 25 the second pressure chamber on the injector side 27 , The first printing room 23 is in a correspondingly enlarged section of the guide bore 65 and partly in the adjacent part of the pipe socket 69 arranged and the second pressure chamber 27 is in a through hole of a connecting piece 73 provided, the injector side in the pipe socket 69 is screwed in and the guide bush 67 axially against a paragraph 75 of the pipe socket 69 braced. In the pipe socket 69 opposite end of the connecting piece 73 is a valve holding body in the embodiment 77 of the fuel injector 7 screwed in, the sealing seat over a conical filler 79 is guaranteed between the valve holding body 77 and connecting piece 73 is axially clamped and has an axial through opening.

Furthermore, between the peripheral wall of the guide bush 67 and the inner wall of the pipe socket 69 an annulus 71 provided the return spring in the third embodiment 37 of the step piston 19 receives. The return spring 37 is supported on the end face of the connecting piece 73 stationary and on the other hand acts on the stepped piston 19 over a bracket 81 towards the pressure chamber 23 , This in the 4 shown in a single part drawing U-shaped bracket 81 has a slot 83 whose dimension corresponds to the smaller diameter of the stepped piston 19 or one at the cross-section transition on the stepped piston 19 provided receiving groove corresponds. The clip 81 protrudes radially through the guide bushing at provided longitudinal slots, not shown 67 and is due to the diameter shoulder of the stepped piston 19 on.

The stroke movement of the stepped piston 19 in the direction of the pressure chamber on the pump side 23 is by a ring heel 85 on the circumference of the guide bush 67 limited, with the return spring 37 the stepped piston 19 moved to this starting position. The pressure chamber towards the injector 27 directed working stroke of the stepped piston 19 is marked by a paragraph 91 the guide hole 65 limited to that of the stepped piston 19 with the bracket 81 comes to the plant ( 3A ).

The filling of the second pressure chamber 27 takes place via one of the first pressure chamber 23 Purging bypass or inlet line through an axial longitudinal hole 87 in the guide bush 67 is formed. Depending on the position of the stepped piston, the further passage of fuel then takes place directly into the end faces of the guide bush 67 limited pressure rooms 23 . 27 or the remaining play between the step piston 19 and the walls of the through holes in the pipe socket 69 or connecting piece 73 , In the longitudinal hole 87 is an in Direction of the pressure chamber on the injector side 27 opening check valve 45 used, in front of a throttle in the flow direction 89 is arranged.

The operation of the third embodiment is analogous to the previous embodiments, the 3A the position of the stepped piston 19 during the working stroke when reaching the end position.

The 3B shows the stepped piston 19 shortly before reaching its starting position, the refilling of the pressure chamber 27 via the inlet channel along the play of the stepped piston 19 in the pipe socket 69 who have favourited Longitudinal Hole 87 and the check valve 45 even before the starting position of the stepped piston is reached 19 can start.

Claims (12)

Fuel injection device for internal combustion engines, with a fuel from a low pressure chamber ( 5 ) via a high pressure line ( 3 ) to a fuel injection valve ( 7 ) promotional high pressure pump ( 1 ) and a hydraulic translation device ( 13 ) between the high pressure pump ( 1 ) and the fuel injection valve ( 7 ) one in a hole ( 15 ) sliding step piston ( 19 ), the end faces of which each delimit a pressure space, a first larger end face ( 21 ) a first with the pump-side part of the high pressure line ( 3 ) connected pressure chamber ( 23 ) and a second, opposite, smaller end face ( 25 ) a second part with the injector side part of the high pressure line ( 3 ) connected pressure chamber ( 27 ) limited and with an inlet channel containing a pressure valve for filling the second pressure chamber ( 27 ) with fuel, characterized in that the in the second pressure chamber ( 27 ) outlet channel from the first pressure chamber ( 23 ) and through a through hole ( 43 ) in the stepped piston ( 19 ) is formed, with the pressure valve closing the inlet channel inside the stepped piston ( 19 ) is arranged, the transmission ratio on the stepped piston ( 19 ) between the larger piston face ( 21 ) to the smaller piston face ( 25 ) should be between 1 and 3, preferably between 1.5 and 2.2. Fuel injection device according to claim 1, characterized in that a fuel filter ( 57 ) - preferably a rod filter or a throttle is inserted into the inlet channel. Fuel injection device according to Claim 1, characterized in that at the cross-sectional transition of the stepped piston ( 19 ) a ring collar ( 29 ) is provided which, with its ring end face facing the larger piston diameter part D1, forms a stop face which can be connected to a bore shoulder ( 39 ) the bore ( 15 ) interacts and its in the Diameter of the smaller piston part D2 facing the ring end face ( 31 ) a spring chamber ( 33 ) in the hole ( 15 ) limited. Fuel injection device according to claim 3, characterized in that one of the stepped piston ( 19 ) preferably coaxially surrounding return spring ( 37 ) in the spring chamber ( 33 ) is clamped, which is supported on a stationary system, the stepped piston ( 19 ) on the end face of the spring chamber ( 31 ) towards the hole shoulder ( 39 ) acted upon and depending on the static pressure in the high pressure line ( 3 ), the piston faces ( 21 . 25 ) and the opening pressure of the pressure valve in the inlet 19 ) between the injections at its pump-side stop ( 39 ) presses. Fuel injection device according to claim 3, characterized in that the fixed spring contact surface on a in the bore ( 15 ) inserted sleeve ( 35 ) is provided. Fuel injection device according to Claim 3, characterized in that the spring chamber ( 33 ) at least one relief line ( 41 ) in the low pressure room ( 5 ) leads away. Fuel injection device according to Claim 1, characterized in that the stepped piston ( 19 ) in a guide hole ( 65 ) a guide bush ( 67 ) is slidably guided into a pipe socket ( 69 ) is used. Fuel injection device according to Claim 7, characterized in that between the guide bush ( 67 ) and the inner wall of the pipe socket ( 69 ) an annulus ( 71 ) is formed, which is a return spring ( 37 ) of the stepped piston ( 19 ) records. Fuel injection device according to claim 8, characterized in that the return spring ( 37 ) with its small end face ( 25 ) of the stepped piston ( 19 ) facing axial face against a stationary stop and with its opposite, the larger stepped piston face ( 21 ) facing the end face a connecting element which the guide bushing ( 67 ) radially protruding at longitudinal slots on the step of the stepped piston ( 19 ) is present. Fuel injection device according to claim 9, characterized in that the connecting element as a U-shaped bracket ( 81 ) is executed. Fuel injection device according to claim 7, characterized in that the guide bush ( 67 ) from one into the pipe socket ( 69 ) screw-in connecting piece ( 73 ) axially against a shoulder ( 75 ) in the pipe socket ( 69 ) is tensioned.